The following steps show how to create a shape tween from frame 1 to frame 30 of the Timeline. However, you can create tweens in any part of the Timeline that you choose. You will be morphing one shape into another shape.
1. In frame 1, draw a square with the Rectangle tool. Fill it with color.
2. Move to frame 35 of the same layer and add a blank keyframe by choosing Insert > Timeline > Blank Keyframe or pressing F7.
3. On the Stage, draw a circle with the Oval tool in frame 30. You should now have a keyframe in frame 1 with a square and a keyframe in frame 30 with a circle.
4. In the Timeline, select one of the frames in between the two keyframes in the layer containing the two shapes. Then, in Properties at the bottom of the Stage select “Tween” and “shape” to create the motion becoming a shape. Flash interpolates the shapes in all the frames between the two keyframes.
5. To preview the tween, scrub the playhead across the frames in the Timeline, or press the Enter key.
To tween motion in addition to shape, move the shape in frame 30 to a location on the Stage that is different from the location of the shape in frame 1. Press Enter. Export as movie file and load on to web page. Additional options:
1.To tween the color of the shape, make the shape in frame 1 a different color from the shape in frame 30.
2.To add easing to the tween, select one of the frames between the two keyframes and enter a value in the Ease field in the Property inspector.
3.Enter a negative value to ease the beginning of the tween. Enter a positive value to ease the end of the tween.
http://help.adobe.com/en_US/flash/cs/using/WS58E1E1A4-9296-4b75-AB74-D9D545892556.html